This invention relates to display apparatus, in particular to stereoscopic visualisation display apparatus of the type in which a stereoscopic image is projected onto a viewing screen and is viewable in stereoscope by an observer wearing special glasses.
Such Stereoscopic, or xe2x80x9c3Dxe2x80x9d, display apparatus is well known in the automotive and architecture fields, and has been used in the aerospace and defence industries. In many applications, stereoscopic projection onto a vertical or wall-mounted screen is common, however for certain applications a more immediate intuitive assimilation of the information contained in the projected image can be achieved when the image is projected onto a table top (i.e. onto a screen which is horizontal, or only slightly inclined thereto).
Such table top displays require substantial headroom above the table in which to mount the projector, and are usually clumsy to install and not readily transportable. Attempts have been made to address these problems using xe2x80x9cback projectionxe2x80x9d arrangements, in which the projector is mounted beneath the table top, which is formed of translucent or semi-transparent material so that the image projected onto the bottom of the table top can be viewed from above. The disadvantage of such systems is that there is only a short xe2x80x9cthrowxe2x80x9d (the distance between the projector and screen), leading to limited spread of image without the use of powerful projection lenses, and also that the intensity of the projected image is considerably attenuated in its passage through the table top xe2x80x9cscreenxe2x80x9d.
In order to address these concerns, the present invention provides a stereoscopic visualisation display apparatus comprising a table having a top onto which a stereoscopic image is projected, a stereoscopic projector closely adjacent to the table and oriented so as to project an image away from the table and towards a reflector so positioned as to reflect the image from the projector towards and onto the table top.
Such an arrangement effectively doubles the projector xe2x80x9cthrowxe2x80x9d, enabling a relatively compact arrangement whilst allowing the image to spread, it also has the advantage that the projector does not need to be supported above the table top, only a relatively light weight reflector. Moreover, although the reflector does result in some attenuation in image intensity this is not so great as in a xe2x80x9cback projectionxe2x80x9d system. Thus, an apparatus in accordance with the invention is capable of producing a high quality image and can be made so as to be easily transportable.
The projector is preferably releasably mounted to the table, and may be releasably received within a collapsible cradle which is fitted to the table and unfolds into position from beneath the table top. The cradle may be designed to unfold into a position such that, when the projector is held thereon, the projector is aligned so as to project an image in a given direction above and away from the table top so as to facilitate the location and orientation of the reflector.
Additionally or alternatively a frame is provided, which may be collapsible and/or integral with the table, which is adapted to hold the reflector generally above the table top. Such an arrangement enables the apparatus to be erected easily and quickly, and the reflector may be mounted to the frame in such a way as to be tiltable about at least one, preferably substantially horizontal axis, and/or movable to a limited degree, in order accurately to align the reflected image onto the table top.
The reflector is preferably a lightweight mirror, and of the type comprising a silvered reflecting surface deposited on a flat plastics substrate. Provision of the reflecting surface on top of the substrate minimises attenuation of the image intensity during reflection, and the use of a lightweight substrate facilitates the support and accurate alignment of the reflector relative to the projector and the table top.